Cleaning of metallic parts



Patented Jan. 5, 1932 UNITED STATES PATENT OFFICE SUMNER BEDWAY MASON,OF WIIMETTE, ILLINOIS, ASSIGNOB T0 WESTERN ELECTRIC I COMPANY,INCORPORATED, OF NEW YORK, N. Y, A OORPOBATION OF NEW YORK (ammo orMETALLIC ran/rs This invention relates to the cleaning of metallic arts,and more particularly to an electrolytic method of cleaning metalllcparts preparatory to electro-plating.

An object of the invention is to clean metallic parts in a thorough,rapid, and economical manner.

In accordance with one embodiment of the invention, any grease adheringto the metallic parts is first removed by immersing the parts in analkali electrolyte while passing an electrical current from the partthrough the electrolyte; scale and oxides are then removed by immersingthe parts in an electrolyte consisting of hydrochloric acid and aninhibitor, such as formaldehyde while passing alternating currentthrough the parts and the electrolyte; and traces of copper or otherforeign substances are then removed by immersing the parts in a cyanidesolution. The parts are passed immediately from the cleaning process toa plating bath.

The invention will be more fully understood from the following example,which illustrates one embodiment thereof. The parts to be cleaned areimmersed in a solution of an alkali, such as sodium hydroxide orpotassium hydroxide, which is maintained at a temperature of about 200F., the preferred concentration being approximately one pound of causticsoda per gallon of solution, and direct current at approximately 50'amperes per square foot of anode surface is passed from the parts to asubmerged cathode during such immersion. When the grease is removed fromthe surfaces of the parts, the parts are then rinsed in water andimmersed inan electrolyte containing hydrochloric acid intheconcentration of approximately 200 grams of hydrochloric acid gas perliter of solution, the bath also contaming about 1% offormaldehyde toprevent attack on the surfaces after the scale and rust have beenremoved by the acid. In this bath alternating current at a concentrationof about 7 5 amperes per square foot of surface to be cleaned is passedbetween the parts and a submerged electrode,iand the electrolyte ismaintained at a temperature of from 85 to 115 F. This acid bath'removesscale and 1929. Serial No. 356,888;

oxides from the parts in about two minutes, and the parts are then againrinsed and immersed in a cyanide solution containing approximately onepound of sodium or potassium cyanide and one-fourth pound of sodium orpotassium hydroxide per gallon of 5%1Q1Ltigfl, the bath being maintainedat about This process is especially adapted to be carried out by the useof automatic machinery whereby the parts are successively passed frombath to bath in timed sequence. In practicing the invention with suchmachinery it will usually be found advantageous to suspend the parts bymeans of copper wires, since copper is but little affected by thevarious electrolytes used with the process. The copper will, however, bedissolved to some slight extent by the hydrochloric acid bath, andtraces of copper may appear on the surfaces of the parts being cleaned.These traces, as well as an other loosely adhering material which mayave adhered to the parts in their passage'through the acid bath, are

removed by the cyanide bath.

The concentrations, temperatures, and other conditions outlined abovemay be considerably varied without departin from the spirit of theinvention as defined y the following claims.

What is claimed is:

T. The process of cleaning metal parts, which consists in immersing.them in a bath containing hydrochloric acid and a small amount offormaldehyde.

2. The process of cleaning metal parts, which consists in immersing themin a bath plonitaining hydrochloric acid and formaldey through the partsand the bath.

'3. The process of cleaning metal parts, which consists in immersingthem successively in a sodium hydroxide solution and a solution ofhydrochloric acid and formaldehyde.

.4. The process of cleaning metal parts, which consists in immersingthem in a sodium hydroxide solution at, a temperature slightly below itsboiling point and then immersin them in a solution of hydrochloric acidan formaldehyde.

and passing alternating current.

ly in a sodium h droxide so 5. The process of cleanin metal parts,

which consists in immersing t em successiveution and a solution ofhydroc oric acid and formaldehyde while passing electrical currentbetween the parts and another electrode.

6. The process of cleaning metal parts, which consists in immersing themin a sodium hydroxide solution while assing direct current from theparts throng the solution, and then immersing the parts ina solution ofhydrochloric acid and formaldehyde while passing alternating currentthrough the solution to the parts.

7. The process of cleaning metal parts, which consists in immersing themin a hot sodium hydroxide solution while passing direct current from theparts through the solution, and then immersin the parts in a solution ofhydrochloric aci and formaldehyde while passing alternating currentthrough the so ution to the parts.

-8. he process of cleaning metal parts, which consists in immersing themsuccessively in an alkali bath, a hydrochloric acid bath containingformaldehyde, and a cyanide 7 bath.

9. The process of cleaning metal parts. which conslsts in immersing themin a sodium hydroxide solution at about 200 F. while passing directcurrent from the parts through the solution, then immersing them in asolution of hydrochloric acid and formaldehyde while passing al atingcurrent through tgern the h drochloric cid solution? to the parts,

and en immersing them in a cyanide solu-' tion at about 160 F.

In witness whereof, I hereunto subscribe my name this 13th da of A ril,A; D. 1929.

SUMNER EDWKY MASON.

